In order for a USB (universal serial bus) host computer to complete a connection recognition of a USB device, a delay which complies with a USB standard for reset completion waiting or address allocation becomes necessary. However, there are some USB devices in the marketplace that do not respond with completing the connection recognition within the delay of a standard value. In order to use a device which does not respond within the delay of the standard value, a delay which is a margin is applied and the standard value to lengthen a response time of the USB device.
For example, Patent document 1 discloses a scheme of adding a margin, by an external input, to a USB device which does not operate within the delay of the standard value.
If it can be recognized as to which device does not operate within the delay of the standard value, a further margin may be added to the delay for a specific USB device. However, this scheme requires knowing individual device operations in advance for all USB devices and is unrealistic. Therefore, in order to cause any USB device to respond, it is necessary to use a delay of a value in which a margin is added, so that it can handle all USB devices. However, this causes a time until device recognition completion to be long relative to a case in which the delay of the standard value is adapted, causing a boot time to be generally delayed.
For example, Patent document 1 discloses adding a margin to a USB device which does not operate within the delay of the standard value, which stands on an assumption that “whichever device does not operate within the delay of the standard value may be recognized for all USB devices”. If this assumption does not hold, inconvenience for a user to add the margin using the external input and a problem of failed recognition of a device at a time of an initial connection can occur.
Moreover, the user does not have any knowledge of the delay, so it is anticipated that a task of adding the margin by the external input is carried out for a first time after a failed recognition of the device. Furthermore, a factor for the failed recognition of the device is not only due to a delay shortage, which could cause the user to misunderstand what the factor is.
Moreover, there may be a case in which a special control scheme is to be applied to a specific USB device, other than a control time (a response time) for the above-described USB device recognition.